Leichtlehm (light loam) is a straw and clay mixture, which after being moistened and pressed between forms, hardens into a strong material. It is typically used for making walls and is an old and durable German technique. While Earthships have the cool sounding name and have the rebel cachet from New Mexico’s Garbage Warrior, are they really suitable for a cold temperate climate? The answer is dependent upon the wall thickness and the building’s ability to store and hold heat.
An updated version of an old German technique known as “Leichtlehm” that was built in Ontario north of Guelph.
Building on high-flying concepts | Toronto Star
WEST GREY, ONT.–If you build an EcoNest they will come.
Not only that, but it seems they will pay $495 (U.S.) for the experience they can gain by helping you build the “EcoNest” – a house made of straw and clay. In this case “they” were 20 people from across Canada who showed up in Grey County for four days at the end of May to attend a straw-and-clay building seminar.
The EcoNest they built belongs to Ernie and Edith Martin, whose Riverstone Retreat Centre has offered quiet getaways for families or corporate groups since the early 1990s. The Martins decided to add a two-bedroom cottage to their stone retreat complex near the town of Durham – about 150 kilometres northwest of Toronto – and wanted to make the new building as environmentally friendly as possible.
The idea to make it an EcoNest came from local timber-frame home builder Joshua Thornton, who had just completed a research report on straw-light clay building for the Canada Mortgage and Housing Corp. Earlier, at a green living symposium, Thornton had met a U.S.-based man named Robert Laporte, who devised the concept for EcoNests. He has been building them for a decade south of the border.
With the Martins’ permission, Thornton invited Laporte and his wife, Paula Baker-Laporte, a graduate of the University of Toronto School of Architecture, to come to West Grey, give a seminar and demonstrate the building method.
Originally a log home builder, Laporte had moved to Iowa from Sudbury two decades ago and found he faced a major challenge: There weren’t many trees. So he looked for alternatives and to his surprise, found inspiration from the birds.
“A bird builds its nest using the materials at hand to create a shelter,” Laporte says. And it turns out there was plenty of straw and clay in Iowa, so Laporte and his wife began experimenting. Using a swallow’s nest as a model, the Laportes came up with a building method they say creates a healthy home environment.
“The average person spends 90 to 95 per cent of their time indoors. Therefore, the home should be a sanctuary that nurtures your body, mind and spirit,” Laporte says. “EcoNests” are made by combining clay, straw, wood chips and water into a slurry that is lightly packed between wooden slipforms. This creates walls that breathe, despite being windproof and offering an insulation value of R24, he says.
Although the wooden slipforms can be removed immediately, it takes about eight weeks for the slurry to dry. The walls are then plastered, using an earth plaster mix, (not cement stucco) inside and out. Laporte recommends wooden siding instead of earth plaster on the exterior in very wet climates.
EcoNests, when completed, look very much like a conventional home. But they provide “a much healthier environment,” says Laporte, who is now living in New Mexico, where he and his wife continue to build the straw-clay homes. What took everyone by surprise was the number of would-be EcoNest builders who responded. Some of the 20 who came on site were in the construction business while others had no building experience but wanted to learn. The fee they paid included instruction and lunch daily.
“The response has been wonderful. There is a huge interest in this building method,” says Thornton, who plans to open a permanent EcoNest training centre in Flesherton (about 60 kilometres southwest of Collingwood). Peggy Frith, 33, who travelled from the Nelson, B.C., area, was impressed. “What I really liked is that it’s so easy to do and once you know how, there are no special skills required,” says Frith, who builds homes in northern B.C.
Dave Zimmermann, a maintenance manager at a Cambridge, Ont., food company, wanted to learn skills so he and his wife Crystal can create their own EcoNest on their two-hectare property. “I had already bought the book,” Zimmermann says, referring to the Laportes’ book, EcoNest, Creating Sustainable Sanctuaries of Clay, Straw, and Timber, published by Gibbs Smith in the U.S.
“Attending the seminar has brought the book to life and I really feel that we can build our own.” Along with fellow seminar attendees, Zimmermann spent four days mixing straw with clay and water to make a slurry. This is then pressed down between slipforms to create the walls of the cottage.
Straw-clay construction is not as fragile as regular straw bale construction and is more fire-retardant and flexible, Thornton says. The straw was grown on the Martins’ 52-hectare property at an estimated cost of about $100 for the seed; much of the clay was also collected from the Martins’ land.
In addition to being cheap, the material is environmentally friendly. And while the process is labour-intensive, costs are similar to those associated with regular building methods. Thornton estimates that an EcoNest costs from $150 to $200 per square foot to build depending on interior finishes, but adds that there are significant savings if the homeowner does his or her own building.The straw-clay mix replaces insulation and forms part of the wall, reducing the amount of framing required (although the straw-clay walls cannot be load-bearing). Thornton says that built properly, a house constructed using light straw clay meets the objectives of the Ontario Building Code.
“The labour is all drawn from the local area, which keeps the money in the local economy instead of bringing in products made elsewhere,” Thornton says. The finishing touch to the walls is a coat of natural plaster applied after eight to 12 weeks of drying.
Much of the material used in the cottage was found on the Martins’ property. The giant beams that form the timber frame are from dead white ash or elm trees hauled out of the forest by a team of horses and milled by a Mennonite sawyer. The foundation is insulated concrete forms made from 78 per cent recycled wood chips.
The cottage has been designed to be energy-efficient by adding shade-producing roof overhangs and cross ventilation in each room. Interior finishes will be natural products such as wood, stone and clay. No vapour barrier is necessary as clay has the ability to hold moisture without deteriorating. It has the ability to wick water away from wood and straw and to release the moisture back into the air when the ambient air humidity drops, Laporte says.
Laporte says there are straw-clay homes that are still standing after 800 years in Germany and he believes an EcoNest will last for centuries. “It’s a handcrafted heirloom that will serve many generations to follow,” he says.
For more information on EcoNests click on econests.com.
To learn how to make any building more sustainable by understanding the principles of energy efficiency, check out “How to Future Proof Your Home: A Guide to Building with Energy Intelligence in Cold Climates.“